This invention relates to a CATV system and a CATV terminal unit for use therein, comprising a head end (center) which re-transmits broadcast waves of existing stations or transmits independently produced programs and a number of terminal units connected to the center via cables.
Conventionally, a center (head end) apparatus in the CATV system of this type comprises a VHF antenna, a UHF antenna, and a BS antenna for receiving broadcast waves of existing stations. The broadcasting signals received by these antennas are respectively processed and mixed before being transmitted via a transmission line, e.g., a coaxial cable.
The center apparatus also comprises sources for independently produced original programs, such sources including a video camera, a video cassette recorder (VCR) or the like. The system selects such sources for transmission of the produced signals via the cable.
The center apparatus determines, according to a broadcasting schedule of programs, from which source the signal is obtained, modulates a TV signal from the selected source to have a specific channel frequency, and mixes the TV signal with other signals before transmitting them via the transmission line.
Further, the center apparatus transmits data, such as a channel and permission or prohibition for receiving a specific program, to a subscriber terminal unit in the form of an FSK signal on a channel prepared in advance.
On the other hand, each CATV terminal unit has an address unique to itself, by which only the terminal unit belonging to a subscriber having a contract to receive chargeable programs is allowed to receive the chargeable programs. Such a terminal unit selects a desired signal from signals transmitted via the transmission line, descrambles the selected signal if the selected signal carries a chargeable program and was scrambled by the center apparatus, and modulates the descrambled signal to have a specific channel frequency of a television receiver, e.g., channel 3 or channel 4, before outputting the signal. The FSK signal transmitted as out-of-band data from the center apparatus is subjected to a predetermined process and then is used to generate a control signal for a control of a descrambling operation.
The CATV terminal unit further comprises an input unit provided in the main body and a remote control unit separately supplied as an input unit. Operation of either input unit activates execution of channel selection, setting operation of a timer (a time at which the terminal unit power is turned on), or the like.
In the above-mentioned general arrangement of a CATV system, the timer function of the CATV terminal unit may sometimes be used as a VCR recording timer, an alarm timer, or a sleep timer.
In the above-mentioned CATV system and CATV terminal unit therefor, when the subscriber uses the timer function of the terminal unit to reserve a program, it is necessary to input such data as the channel number of the program, the date, the turning-on time, and the turning-off time. This is a cumbersome operation involving a number of steps.
On the other hand, the actual broadcasting time of a "realtime" program such as a sporting event or other live programming may be subject to change due to a change of the start time or end time of the event. If a timer reservation has been set to such a program, but the actual starting or ending time is different from what was scheduled, it may occur that the timer-on function will be activated when the reserved program has not yet started. In this case, the subscriber typically waits before the TV receiver for the reserved program to start. Alternatively, it may occur that a part of the program will be missed because of the difference between the times selected by the timer unit and the actual broadcast time of the program.